League of Legends guide for a beginner: what is a champion?

Champion statistics – offensive stats

There are eight main types of offensive statistics: attack damage, attack speed, critical strike chance and damage, armor penetration, ability power, magic penetration, life steal and spell vamp, and lethality. Here’s a brief explanation of each.

Attack Damage (AD): How much damage your champion does when it uses a basic attack.
Attack Speed (AS): How fast your champion will finish the animation of their basic attacks (finishing the animation quicker allows more attacks in a given time).
Crit chance/damage (Crit): Crit chance modifies the chance that one of your champion’s basic attacks will crit and do twice the normal amount of damage. However, crit damage modifiers will increase that amount of damage done on crits.
Armor penetration (Pen): The amount of armor that your attacks ignore.
Ability power (AP): Also known as magic damage, the amount of damage your abilities will do. However, a lot of champions don’t have abilities that improve with more ability power, making this stat useless on them.
Magic penetration (Magic Pen): The amount of magic resist that your attacks ignore.
Life steal and spell vamp: The amount of damage your attacks will heal you for. Life steal only refers to healing from damage done by basic attacks, while spell vamp is damage done via abilities.
Lethality: A type of armor penetration that scales up with your champion’s level.